Sequential assimilation of multi-mission dynamical topography into a global finite-element ocean model S. Skachko1,*, S. Danilov1, T. Janjić1, J. Schröter1, D. Sidorenko1, R. Savcenko2, and W. Bosch2 1Alfred Wegener Institute for Polar and Marine Research, Bussestrasse 24, 27570 Bremerhaven, Germany 2Deutsches Geodätisches Forschungsinstitut, Alfons-Goppel-Strasse 11, 80539 Munich, Germany *now at: Département des Sciences de la Terre et de l'Atmosphère, Université du Québec à Montréal, C. P. 8888 Succ. Centre-ville Montréal, Québec, H3C 3P8 Canada
Abstract. This study focuses on an accurate estimation of ocean circulation via
assimilation of satellite measurements of ocean dynamical topography
into the global finite-element ocean model (FEOM). The dynamical
topography data are derived from a complex analysis of multi-mission altimetry data
combined with a referenced earth geoid. The assimilation is split into
two parts. First, the mean dynamic topography is adjusted. To this end
an adiabatic pressure correction method is used which reduces model divergence from the real evolution.
Second, a sequential assimilation technique is applied to improve the
representation of thermodynamical processes by assimilating the time
varying dynamic topography. A method is used according to which the
temperature and salinity are updated following the vertical
structure of the first baroclinic mode. It is shown that the
method leads to a partially successful assimilation approach reducing
the rms difference between the model and data from 16 cm to 2 cm.
This improvement of the mean state is accompanied by
significant improvement of temporal variability in our analysis.
However, it remains suboptimal, showing a tendency in the forecast phase
of returning toward a free run without data assimilation. Both the
mean difference and standard deviation of the difference between the forecast
and observation data are reduced as the result of assimilation.
Citation: Skachko, S., Danilov, S., Janjić, T., Schröter, J., Sidorenko, D., Savcenko, R., and Bosch, W.: Sequential assimilation of multi-mission dynamical topography into a global finite-element ocean model, Ocean Sci., 4, 307-318, doi:10.5194/os-4-307-2008, 2008.